This invention relates to a process of preparing biotin from L-(+)-cysteine. Biotin, vitamin H, is a natural product found largely in the kidney, liver, egg yolk, milk and yeast. The compound is used to prevent symptoms of egg-white injury in experimental animals. Its prime medical use is in various dematitides.
Biotin has been prepared synthetically by Harris et al. (Science, 97, 447 (1943) and Baker et al. (J. Org. Chem., 12, 167 (1947), among others. None of these syntheses, however, were commercially feasible. The first commercial synthesis of biotin resulted from the work of Goldberg and Sternbach (U.S. Pat. Nos. 2,489,235 and 2,489,236).
Previous biotin syntheses suffer from the disadvantages that racemic mixtures of intermediates, as well as racemic mixtures of biotin, are formed thus requiring costly and time consuming resolutions. These resolutions also lead to decreased yields of biotin. This disadvantage is obviated in the instant invention by use of cysteine as the starting material. Cysteine, a natural amino acid is an optically active compound with the same absolute configuration as the C.sub.4 -carbon of d-biotin, the biologically active form of biotin. The process of the instant invention proceeds without racemization in forming d-biotin, thus obviating the need for resolution of the final product.
According to the instant invention, biotin is obtained in either the optically pure d-form or as a racemic mixture from a relatively inexpensive starting material. When d-biotin is obtained the need for chemical resolution is obviated. However, in instances where the racemic product is prepared the d-biotin is obtained by conventional resolution procedures.